Assessment of homozygosity and fertility in meiotic gynogens of the European sea bass (Dicentrarchus labrax L.)

Analysis of 5–6 microsatellite loci was used to measure the increment of homozygosity in two meiogynogenetic progenies (A and B) of sea bass with respect to their mother. In progeny A and B, 20% and 12% of the meiogynogens retained heterozygosity for all investigated maternal loci, respectively, while complete homozygosity was observed only in 6% of B and in none of A, indicating the occurrence of significant allelic recombination during meiosis. The overall increment of homozygosity for the investigated loci was 27% for A and 47% for B. Although survival at hatching of meiogynogens was about half that of controls, they subsequently grew as controls and displayed the same onset of puberty and reproductive potential at adulthood during three consecutive years when crossed between themselves (11 crosses) or with control fish (13 crosses). In particular, meiogynogenetic females (n=24) underwent vitellogenesis and yielded eggs of good quality upon stimulation with LH–RH analogue similarly to normal fish. Sperm released by meiogynogenetic males (n=23) was equivalent to that of controls in terms of volume, quality and fertilization capability. Second generation meiogynogens were obtained by chromosome set manipulation from meiogynogenetic females and found to be morphologically normal at 3 years of age. Interestingly, under our culture conditions, the percentage of meiogynogenetic males in the second generation was 7% as opposed to 39% in the first generation.